It has long been known in the art that an autostereoscopic, three-dimensional, volume display can be created by imposing a two-dimensional image on an imaging surface, or display screen, and then rapidly moving the imaging surface along a third axis.
In the method of imaging known as angular multiplaning, the display screen is rotated about an axis so oriented as to cause the image on the screen to sweep through the desired volume of space. One such system is found in Ketchpel, U.S. Pat. No. 3,140,415 which utilizes a phosphorescent rotating screen being illuminated by fixed electron gun means. Serious drawbacks to such a system, related to the lag time of the phosphors, have been discussed in detail in Muckerheide, U.S. Pat. No. 4,799,103. Additional drawbacks to such a system arise from the requirement of enclosing the screen and electron gun means in a vacuum. Muckerheide also discusses the evolution of the art towards incorporating lasers as image generation sources. Currently, such use of lasers is widely practiced.
A three-dimensional, volume image created by a rotating display screen system is limited to only occupying the volume of space which is swept by the rotating screen. If, for a flat display screen, the axis of rotation does not lie in the plane of the screen, but rather passes obliquely through it, then blank, non-addressable conic spaces, determined by the angle of the display screen relative to the axis of rotation, will appear, thus reducing the overall volume of space in which the image may be generated. Such a system is disclosed by F. Garcia, Jr. in U.S. Pat. No. 4,871,231. Unfortunately, the display created by this system is limited to an addressably incomplete spatial or cylindrical volume due to the restriction that the axis of rotation must pass obliquely through the plane of the screen.
Helliwell, "`Fish Tank` Display Creates True 3-D Images," PC Week, V. 6, Sep. 25, 1989, p. 19 (1), describes a similar system designed by F. Garcia, Jr. and D. Williams of Texas Instruments in Dallas, which attempts to solve the above-identified problem by incorporating a double helix shaped rotating screen. Although the screen in this system sweeps a complete cylindrical volume, a blank cylindrical space, inaddressable by the image light, still exists along the axis of rotation, thus once again limiting the display space to an incomplete cylindrical volume. Also, due to the irregular surface of the double helix screen, the system requires complicated and costly scanning techniques and computing sofware which lengthens the time between data acquisition and display. While helically-shaped screen displays are theoretically potentially fully addressable, they will require a plurality of scanners to achieve such full addressability. This requirement will further increase the overall size and expense of the system.
Another inherent problem with rotating screen displays is the inconsistency of image brightness at various viewpoints relative to the position and shape of the screen. This phenomenon is due to the minimal amount of light which is scattered off of the screen at angles to the plane of the screen which approach zero degrees. Whenever an eye of the observer falls in the plane of space defined by the rotating screen, virtually no image light reaches that eye, thus creating a blank area. Some amount of natural compensation for this problem occurs due to the horizontal parallax between the eyes of the viewer; however, this partial solution is dependent upon the binocular vision of the viewer, the nature of the screen, and the viewer's distance from the display.
Another problem with three-dimensional volume displays is the inability of images in the display to exhibit optical traits known to physical objects. Such traits include, but are not limited to, the reflection of light off of surfaces of objects, the refraction of light through lenses, and the inability to see the rear surface of an opaque solid object. It is well known in the art that volume display images possess a "ghost-like" transparent quality.
Accordingly, it is an object of the invention to minimize the above problems by providing a rotating flat screen fully addressable volume display and system utilizing a rotating flat screen in which the axis of rotation lies in the plane defined by the screen, and where the image light may be addressed onto all points of the screen at all angular positions.
It is an additional object of the present invention to provide a display screen which evenly distributes the intensity of image light reflected off of and transmitted through the screen at all angles to the optical axis of the projected image.
It is a further object of the present invention to provide a means for simulating in three-dimensional images the same optical qualities existing in physical objects, such qualities corresponding to the specific viewpoint of the observer relative to the position of the display.
It is a still further object of the present invention to provide a display screen which minimizes drag due to wind resistance, thereby allowing for larger three-dimensional displays and faster display screen rotation.
It is further object of the present invention to provide provide laser beams of different colors, where various colored laser beams may be combined with one another to generate blanking techniques which can eliminate or alternatively enhance specific characteristics of the three-dimensional presentation.
It is another object of the present invention to provide a three-dimensional system which can store preselected images and rapidly access and display, modify, and/or enhance such images in accordance with variations in the data input signal. The persistence of vision of the human observer thereby will cause the discrete three-dimensional images to fuse together, thus forming a three-dimensional "movie" in real time.
It is yet another object of the present invention to provide a three-dimensional biofeedback display system in which the data input signal is a function of the three-dimensional display image. This implementation of imagined spatial operations, or "spatial thinking," towards the acute self-control of specific physiological processes would be extremely valuable in biofeedback training. In one application, a biofeedback subject who has gained sufficient skills through practice with such a three-dimensional biofeedback display system might be able to control a cursor in the three-dimensional display or pull up specific stored images for display. Such skills would be of immeasurable benefit to victims of paralysis.
It is yet another object of the present invention to provide an inexpensive and easily operable three-dimensional system capable of functioning without the aid of a computer, whereby the image control signals are themselves a function of the image to be ultimately displayed.
It is yet a further object of the present invention to provide specific mathematical functions to be applied to the image signals towards the correction of unwanted distortion or skewing in the final three-dimensional display.
It is yet another object of the present invention to provide a three-dimensional display system, or "theater," for the objective viewing of, and interaction with, Virtual Reality.
It is yet another object of the present invention to provide a fully addressable three-dimensional display system including a rotating flat screen wherein a single scanner is used to address all points in the image volume.